Oh, DS9 ruined Worf's entire family. They did even worse to Kurn.
Alexander appeared in DS9 four years after he appeared in TNG, and in that time he'd aged about ten years and dropped about 50 IQ points. He wasn't that great a character in TNG but he was an oversensitive kid with violent tendencies, not just a one dimensional incompetent.
I thought it was refreshing to have a Klingon who wasn't a clone of all the other Klingons. It was the way the Klingons as a race were depicted that was two dimensional, not Alexander. He had human ancestry and had been raised by humans. As with his mother, who was a hybrid, he didn't really fit anywhere but he tried to.